Tens of millions of people today are living part of their life in a virtual world. In places like World of Warcraft, Second Life, and Free Realms, people are making friends, building communities, creating art, and making real money. Business is booming on the virtual frontier, as billions of dollars are paid in exchange for pixels on screens. But sometimes things go wrong. Virtual criminals defraud online communities in pursuit of real-world profits. People feel cheated when their avatars lose virtual property to wrongdoers. Increasingly, they turn to legal systems for solutions. But when...